Astrophotography with a 20D (and a budget)

I've been taking wide field shots using my EOS20D and my Tamron

28-300mm F3.5-6.3 lens (at its widest setting), my tripod, and a

shutter release cable.

I've had acceptable results keeping the aperture open wide, using 1600

ISO, and 30 second exposures.

I would like to break through the '30 second barrier' (using the bulb

setting) but anytime I've done this I end up getting star trails, not

dots.

My research on astrophotography on the Internet reveals two things. I

can build a wooden contraption that requires manual adjustment (a barn

door, I think they call it) or I can spend a gazillion dollars on a

fancy motor driven telescope mount.

I'm only interested in taking the next step so I don't want to invest

big dollars. I'm also not that handy so the homemade option is less

appealing to me.

Is there a reasonable, relatively easy to use, commercially available

motor drive that will allow me to take longer exposures in the several

hundred dollar range? I'd ideally want something that I can mount on

my tripod.

Thanks,

-Mike

Commercial tracking motors are available at

http://www.telescope.com/jump.jsp?itemType=CATEGORY&itemID=26

but can run a little on the expensive side. You can also build your own. Do a search for a Barn Door Drive or Barn Door Mount. This is a homemade, or DIY, astrophoto tracking device. All that is needed is a small motor and you can track the stars for astrophotos.

Good luck.

Digital cameras designed for long exposure astrophotography are actively cooled to prevent thermal noise building up in the chip (check out SBIG for example). The best way to use a dSLR is to take multiple shorter exposures and stack them afterward. This guy does it with a 10D

http://www.ricksastro.com/Gallery/htm/10D.htm

although he is using a high-end set up, which doesn't help you. You aren't going to find anything good that you can mount to your current tripod (photo tripods just aren't heavy enough to damp out the vibrations for this purpose). I haven't used this mount myself, but it would probably work pretty well:

http://www.telescope.com/shopping/product/detailmain.jsp?itemID=376&itemType=PRODUCT&iMainCat=6&iSubCat=24&iProductID=376

You would need the motor drives that Brian mentioned, plus the 1/4-20 adapter and probably the polar alignment scope. If you got it reasonably well aligned and stuck to lenses less than, oh, say 135mm you should be able to do several-minute exposures without the tracking errors becoming visible.

One of the problems I have found with piggyback astrophotography (which is essentially what you're doing here) is finding lenses that you can use wide open without nasty aberrations on the stars in the corners of the frame. I suppose with digital it might not be as bad as with film. The Sigma EX 105mm Macro is excellent in this area (I don't know which Canon lenses are good). Wide fast lenses usually require stopping down 2 or 3 stops to get decent corners.

In case you haven't seen this already, check it out:

http://web.canon.jp/Imaging/astro/index-e.html

http://www.astropix.com/HTML/M_DAP/TOC_DAP.HTM

Good luck.

Thanks Brian and Jerry,

Your responses put me a lot closer to an answer, but unfortunately it would seem that I won't be able to do this given my current budget. I think I'll keep an eye on ebay to see if I can't find a bargain.

Thanks again,

-Mike

Look for a used mount on www.astromart.com. You should be able to get something like a CG-5 or an Orion Skyview Pro or similar mount within your price range.

Another thing you might try is stacking multiple short exposures.<div></div>

There are some inexpensive tracking telescopes you can invest in that automatically track and support astrophotography. However, most of the inexpensive tracking mounts cannot support the weight of a 20D or even an XT. I purchased a 650mm tracking telescope and when I put my camera on it it swings straight up. Not very useful for something on the horizon.

There are a lot of different options, I learned a lot just by shopping for telescopes and camera mounts and all that.

A